Implantable drug infusion therapy has been used to treat various ailments including pain management and diabetes. These drug pumps and delivery systems have been used to deliver pain medication, hormones such as insulin, and other pharmaceutical agents. For example, intraspinal drug delivery may be used to treat chronic pain. By utilizing these systems, pharmaceutical agents are delivered in relatively lower doses to a specific region of treatment. In this manner, full body dilution and membrane barriers are avoided. Similarly, insulin may be delivered without the inconvenience of injections.
Infusion pumps come in several varieties. Some infusion pumps are constant rate such as those driven by gas pressures or springs. Others are variable rate pumps driven by hydration of an expandable substance or a variable rate pumping mechanism.
Implantable drug delivery systems have several advantages over external drug pumps, oral medications, suppositories, and injections. These implantable systems are unobtrusive, unencumbering, and typically deliver smaller doses to targeted regions. Pills, suppositories, and injections deliver large doses of pharmaceutical agents that pass through a large portion of the body to reach the treatment area. The large dilution ratio caused by this passing requires a large dose to achieve an effective concentration in the treatment area. In addition, patients must remember to administer the correct dose at the appropriate time to achieve the desired therapeutic levels of the pharmaceutical agent in the treatment area.
While external infusion pumps overcome some of the limitations of pills, injections, and suppositories, they are often cumbersome and inconvenient. These devices must typically be worn or strapped to the patient, encumbering clothing selection and presenting a risk of damage to the external pump. In addition, catheter incision points are subject to infection.
However, current versions of implantable infusion pump systems also have disadvantages. Typically, implantable infusion pump systems provide limited programmability and patient control. In addition, access to the pump system is limited. Some pump systems have a constant rate while others attempt to control flow rates by varying pump speeds or hydration rates. In the case of constant rate pumps, prescription rates are set by the selected flow restrictor and pump pressure. In the case of variable rate pumps, prescriptions are limited by the available rate settings associated with the pump.
Patients generally have no control over the prescription. In pain management cases, this can lead to periods of under dosing and periods of unnecessary over treatment. Doctors are also limited in the selection of prescriptions and often must have an office visit with patients to adjust prescriptions. These adjustments are expensive to insurance companies, unprofitable for doctors, and inconvenient for patients.
In the case of other treatments such as insulin treatment, the required prescription varies with the behavior and environment of the patient. Insulin requirements increase with carbohydrate laden meals and decrease with activity. Excess insulin can lead to shock and low insulin can lead to excess blood sugar levels and many long term health problems.
Another problem with implantable infusion pumps is determining actual dosage rates and predicting reservoir levels. Limited access to the pump means expensive preemptory refilling. Typical implantable infusion pumps do not maintain rate data useful in determining actual dosage schedules and reservoir levels. Therefore, doctors have difficulty predicting reservoir levels. This often leads to wasted pharmaceutical solution. Worse, the reservoir may empty and patents may suffer from a lack of treatment.
A further problem with current dose control systems lies in their method for controlling dose rates. These methods often use many mechanical parts that may wear. Further, these systems use parts that may malfunction under externally applied magnetic fields such as those of an MRI.
As such, typical infusion pumps suffer from deficiencies in providing prescription options, actual prescription rate data, and control of dosage. Many other problems and disadvantages of the prior art will become apparent to one skilled in the art after comparing such prior art with the present invention as described herein.